Standoff determination

Abstract

In some embodiments, methods, apparatus, and systems may operate to determine downhole tool standoff using a nuclear tool and photon activity, and to correct acoustic measurements using the standoff. Additional apparatus and systems, as well as methods, are disclosed,

What is claimed is: 
     
       1. An apparatus, comprising:
 an array of X-ray detectors mechanically coupled to a collimator to determine standoff to a borehole based on photon activity measured by the array; 
 an ultrasonic transducer to measure a measured distance in mud in the borehole; and 
 a processing unit to correct the measured distance to provide a corrected distance in the mud according to the standoff. 
 
     
     
       2. The apparatus according to  claim 1 , wherein the array of X-ray detectors comprises a complementary metal-oxide semiconductor material arranged in a pixelated format. 
     
     
       3. The apparatus according to  claim 1 , wherein the array of X-ray detectors comprises a substantially linear arrangement of detector elements. 
     
     
       4. The apparatus according to  claim 1 , wherein the collimator comprises an array of tubes to direct photons engaged in the photon activity in the mud to the array of X-ray detectors, and wherein each of the tubes are disposed at a substantially similar angle to the array of X-ray detectors. 
     
     
       5. The apparatus according to  claim 1 , further comprising:
 tubes in the collimator arranged in a substantially similar orientation to provide a plurality of different travel path lengths, as measured along an energy path created by a single source of energy, for photons associated with the photon activity and received by the array. 
 
     
     
       6. The apparatus according to  claim 1 , further comprising:
 a source of energy to direct the energy into the mud, to generate the photon activity. 
 
     
     
       7. The apparatus according to  claim 6 , wherein the source of energy comprises an X-ray tube. 
     
     
       8. A system, comprising:
 a tubular member; 
 an array of X-ray detectors attached to the tubular member and mechanically coupled to a collimator to determine standoff to a borehole based on photon activity measured by the array; 
 an ultrasonic transducer to measure a measured distance in mud in the borehole; and 
 a processing unit to correct the measured distance to provide a corrected distance according to the standoff. 
 
     
     
       9. The system according to  claim 8 , wherein the tubular member comprises an ultrasonic logging tool. 
     
     
       10. The system according to  claim 8 , wherein the tubular member comprises one of a wireline tool or a drilling tool. 
     
     
       11. The system according to  claim 8 , wherein the processing unit is to determine the corrected distance based on energy loss due to beam spreading. 
     
     
       12. A method, comprising:
 determining downhole tool standoff using a nuclear tool and photon activity; and 
 correcting acoustic measurements using the downhole tool standoff. 
 
     
     
       13. The method according to  claim 12 , wherein correcting the acoustic measurements further comprises:
 adjusting the acoustic measurements for beam spreading. 
 
     
     
       14. The method according to  claim 12 , wherein using the nuclear tool further comprises:
 measuring the photon activity using an array of photon detectors. 
 
     
     
       15. The method according to  claim 14 , wherein measuring the photon activity further comprises:
 calculating a ratio of the photon activity for adjacent ones of the photon detectors. 
 
     
     
       16. The method according to  claim 15 , further comprising:
 determining a location of a layer boundary based on a change in the ratio. 
 
     
     
       17. The method according to  claim 16 , further comprising:
 determining thickness of the layer based on the location of the layer boundary. 
 
     
     
       18. The method according to  claim 12 , wherein correcting the acoustic measurements further comprises:
 adjusting a particular one of the acoustic measurements using the downhole tool standoff corresponding to the particular one of the acoustic measurements to provide an adjusted measurement; and 
 repeating the adjusting for additional ones of the acoustic measurements. 
 
     
     
       19. The method according to  claim 12  further comprising:
 directing energy comprising X-rays, using a single source of the energy attached to the nuclear tool, into mud downhole; and 
 determining the downhole tool standoff by counting Compton backscattering events associated with the photon activity created by interaction of the energy and the mud, wherein the Compton backscattering events are monitored along an angle to the nuclear tool. 
 
     
     
       20. The method according to  claim 12 , wherein determining the downhole tool standoff further comprises:
 averaging a plurality of standoff distances corresponding to a plurality of photon travel path lengths determined by a collimator mechanically coupled to an array of detectors in the nuclear tool.